1. Field of the Invention
The present invention relates to the field of jet engines and targets the suspension of the latter on the structure of the aircraft that they propel.
2. Description of the Related Art
A propulsion engine, such as a jet engine, can be mounted at various points on the aircraft by attachment to a strut or a pylon belonging to the structure thereof. It can thus be fixed to the wings, to the fuselage, generally at the rear, or mounted in the tail group by appropriate attachment means. The function of these attachment means is to ensure the transmission of the mechanical forces between the engine and the structure of the aircraft.
The loads to be taken into consideration are oriented in the three main directions of a coordinate system linked to the engine. These are, in particular, in normal operation, the weight of the engine on the vertical axis Z, its thrust on the axis X of the engine, and the lateral aerodynamic loads on the transversal axis Y. The loads to be transmitted also include the take-up of the rotational torque around the axis X of the engine. These means must also allow for the deformations undergone by the engine during the different phases of the flight resulting, for example, from the dimensional variations due to the thermal stresses.
The link between the engine and the strut is usually provided, for fan engines, by two suspension planes, one at the front of the engine, on the intermediate case, the other at the rear. Each of the suspension means is arranged to transmit a portion of the forces. For example, one of the suspensions, called front suspension, takes up or transfers the lateral forces on the axis Y and vertical forces on the axis Z, and that of the engine torque around the axis X. The other suspension, called rear suspension, transmits to the strut of the aircraft the lateral and vertical forces. The axial forces can be taken up by one of these two planes. Such a suspension is isostatic.
With reference to FIG. 1, there is known, through the application EP1707487 A1 from the company SNECMA, a rear suspension 1 comprising a beam 11, possibly double, fixed to the strut by bolts and linked to the case of the engine by link rods 12. The link rods 12 swivel at their ends on clevises or cleats, depending on the mounting, which are attached respectively to the engine case and to the beam 11. This suspension 1 transmits the forces and the moment on the axis Y and the forces and the moment on the axis Z.
In order for the transmission of the forces by the link rod 12 to be purely axial, that is to say, along the axis of the link rods, a swivel bearing 13 is provided at each end of the link rods 12. This mounting makes it possible in particular to absorb the radial and axial expansions of the engine.
The safety constraints also stipulate the presence on this suspension of means mitigating the failure of a force transmission member. Thus, there are usually provided for this purpose link means with play, said to be on standby, which become active by absorption of the play and transmit the forces via a backup pathway, if one of the transmissions fails following a part breakdown. Still referring to FIG. 1, the rear suspension 1 includes a safety link 14 linked at its end to the beam 11 by a swivel-type bearing 13.
Because of the swivel links 13 that the beam 11 has, said beam has a large lateral dimension in the direction Y which disturbs the circulation of the airstream in which the suspension is placed, and in particular the secondary stream for a bypass engine. For a suspension, a beam width D, represented in FIG. 1, is defined, which corresponds to the smallest lateral dimension of the beam 11 which is situated in the airstream. The greater the width D of the beam 11, the more the aerodynamic efficiency of the engine is reduced.
Several beam shapes have been considered for reducing the width D of the beam, but these tests have come to nothing. The swivel-jointed links, which are positioned on the beam, impose a minimum lateral dimension. One immediate solution would be to place them vertically. This is difficult given the fact that the height of the beam is limited. In fact, it depends on the constraints of wing height and engine height relative to the ground which are predetermined. In other words, the current solutions do not allow for the incorporation of swivel-jointed links in a beam whose dimensions are reduced both widthwise and heightwise.